A wide variety of tamper-evident seals have been developed for sealing containers of many types. Many of them utilize relatively expensive materials, and the processes required to make them, and then to affix them to containers in their tamper-evident relationships are expensive. It is with an improved tamper-evident seal and method of making same, and with an expeditious method and apparatus for forming and applying such improved seals, with which the present invention is concerned.
Typically the materials from which one class of tamper-evident seals are made are shrinkable plastic materials, most commonly heat-shrinkable materials. Generally the object so to be sealed is a container having a closure associated with the top portion of the container which may comprise a neck and mouth thereof. Although cork-type closures in container mouths are sometimes so sealed, most such containers utilize closures which are screw-threaded or snapped over the container mouth, thereby to close the top of the container. An effective tamper-evident seal is one which embraces the closure, which envelopes a top peripheral portion of the closure, and which also grippingly embraces the portion of the container immediately below the closure, such as a neck portion of the container. The seal should be of such a material which, when access to the container has been gained, will either have been destroyed or will not readily be reaffixable to the container, thereby to make it evident to a purchaser that the container has been opened, i.e., tampered with.
Plastic materials of different types have been used for this purpose. Indeed, seals of other materials such as lead seals, have been used, such as with wine bottles for this purpose. Usually, when plastic materials are used, tubular bands are formed and are placed over the closure and container in the zones of securance, and the bands are shrunk in place. Shrinking processes most frequently employ heat which requires that the band be shrinkable inwardly, thereby readily to grip the closure and the adjacent container portions. To facilitate shrinking, the tube must be processed to have a shrinking characteristic. Although some materials may be swollen for subsequent heat-shrinking, most commonly the band to be shrunk is formed of an oriented plastic material which, when heat is applied, will shrink primarily in the direction of orientation, i.e, in the radial direction and inwardly of the closure and container portion it is to embrace.
One of the most broadly used processes for so orienting heat-shrinkable materials is to produce sheets or strips and, during their formation, to orient such sheets or strips so that they have a substantial degree of orientation (hence heat shrinkability later) in the machine direction. Such strips or sheet materials may be printed or otherwise decorated. They are usually severed into segments of predetermined rectangular dimensions. The segments are then formed into bands, as by overlapping and adhering marginal edges, and such a band is then applied to a container and closure, and shrunk to form a tamper-evident seal.
In such a process, the direction in which the plastic material is shrinkable is in the direction in which it was formed. If a tube were to be formed continuously in that direction, and segments of the tube removed, the resulting segments or bands would not heat shrink primarily inwardly of the container and closure, i.e., primarily radially but rather would shrink longitudinally. As such, bands formed from the formed, oriented plastic sheet material have become useful as tamper-evident seals only when segments are first cut from the sheet or strips, and the segments are then formed into tubular bands individually.
Other processes have also been used for making tamper-evident bands, but none has combined both ease of formation of the seal and ease of application of the seal in a simple, inexpensive and, when desired, continuous process.